1. Indian Ocean Tsunami of 2004 “The Great Wave” by Katsushika Hokusai (ca. 1823–1829)

2. The Tsunami Also called seismic sea wave Generated by an undersea geologic event, such as a great earthquake, volcanic explosion, or underwater landslide “Tsunami” in Japanese means “harbor wave” Tsunamis are not “tidal waves”

3. Subduction Zone Earthquake Oceanic crust collides with continental crust and is forced downward Compression forces build until rock fractures and an earthquake occurs Graphic © Strahler/Wiley 2005

4. Generation of the Tsunami During the earthquake, the seafloor moves upward, creating a water wave that spreads outward. Graphic © Gerard Fryer 2003

5. Undersea Landslide or Slump Body of sediment slumps downward along a continental shelf Can be triggered by an earthquake Water drops at head of slump, rises at toe to create a wave Wave moves outward as a tsunami Graphic © Gerard Fryer 2003

6. Volcanic Explosion The explosive eruption of Krakatau in August 1883 created a tsunami that claimed more than 36,000 lives

7. The Tsunami Wave The tsunami wave has a wavelength of 100–200 km with a deep water height of 1 m or less Travels as fast as 200 m/s (440 mi/hr) in open ocean As it approaches the shore, it slows, steepens, and rises in height Deep ocean Shoaling

8. The Wave Keeps Coming The wave acts like a temporary rise in sea level, pushing water far inland before it retreats

9. Indian Ocean Tsunami of December 26, 2004 Caused by 9.0 earthquake beneath Java Trench, west of Sumatra, Indonesia Fourth largest earthquake since 1900 1000 km of fault ruptured and sea floor moved upward by about 5 m (16 ft) Sumatra Java Trench

10. Propagation of the Tsunami Wave

11. Banda Aceh, Sumatra, Indonesia Courtesy of DigitalGlobe June 23, 2004

12. Courtesy of DigitalGlobe Banda Aceh, Sumatra, Indonesia Dec 28, 2004

13. Kalutara Beach, Sri Lanka Courtesy of DigitalGlobe Jan 1, 2004

14. Kalutara Beach, Sri Lanka Courtesy of DigitalGlobe Dec 26, 2004

15. Kalutara Beach, Sri Lanka Courtesy of DigitalGlobe Dec 26, 2004

16. Kalutara Beach, Sri Lanka Courtesy of DigitalGlobe Dec 26, 2004

17. The Tsunami’s Toll Deaths: >210,000 –Indonesia: 166,000 –Thailand: 5,000 –Sri Lanka: 30,000 –India: 10,000 Damage: >$7 billion –Indonesia: $4.4 billion –India: $1.5 billion –Sri Lanka: $900 million Aid Donations: >$6.5 billion –Government pledges: $5.3 billion –Private donors: $1–2 billion